The invention relates to subsurface hydrology and engineering geology and, in general, the invention concerns a borehole testing apparatus for conducting hydrologic tests and researching the mechanisms controlling fluid movement and chemical transport in fractured rock aquifers.
Study of the subsurface beneath the ground to identify the quantity and quality of ground water and characterize the movement of contaminants in the subsurface is a concern of many Federal and state regulatory agencies which are responsible for ground-water resources and for the oversight of ground-water remediation. Such study is needed to ensure that technically feasible regulatory decisions can be made. It is also of interest to government agencies responsible for remediation of property. For example, the U.S. Geological Survey routinely conducts cooperative investigations with other federal agencies and state and local governments involving the characterization of ground-water quantity and quality and the migration of contaminants in the subsurface, requiring the hydrologic testing and the collection of water samples from subsurface boreholes for geochemical analysis. Furthermore, many private engineering companies are engaged in similar types of site characterization for corporate clients engaged in the remediation of contaminated ground water.
Hydrologic testing and the collection of water samples for geochemical analysis have often been conducted using downhole equipment to isolate and test water in a discrete interval in a borehole. Individual components used in borehole testing and geochemical analysis, such as pumps, borehole packers, pressure transducers and various types of data acquisition equipment are available from a number of manufacturers.
Commonly, a borehole is drilled into the ground to allow access to the subsurface and testing equipment is lowered into the borehole. In most cases, the borehole equipment is constructed for a specific type of test or geochemical sampling and is typically fixed in place. However, a site may require more than a single type of test to adequately study the site. Further, the physical dimensions of the borehole equipment and the need for various peripheral components at land surface for data collection make such borehole testing equipment cumbersome and not readily transportable from site to site. This is disadvantageous because testing at more than a single borehole, sometimes a series of boreholes, is frequently necessary to characterize a ground-water site.
Therefore, there is a serious need in the art for an integrated borehole testing equipment design which is capable of isolating and testing a discrete interval of a borehole, and which is transportable, easily assembled, and capable of conducting multiple types of hydrologic tests as well as collecting water samples for geochemical analysis. Moreover, with the increased need in recent years for remediation of contaminated ground water, there is an increased interest in equipment which can conduct testing of contaminated ground water. However, the application of downhole equipment capable at isolating a discrete interval of a borehole for hydrologic testing or geochemical sampling at sites having contaminated ground water has not been actively considered because of problems, such as the contamination of the downhole equipment. Therefore, there is a further need in the art for testing equipment that can operate in contaminated ground-water sites.
Prior art of interest includes U.S. Pat. Nos. 5,934,375 (Peterson); 4,435,843 (Jageler); and 3,799,733 (Ringgenberg). The Peterson patent discloses a deep well system for obtaining artesian samples. The system comprises a borehole packer, a pump for withdrawing fluids, and a sample chamber for holding the fluids. A portion of the sample is discharged to flush the system, but the system does not discharge tracer fluid into the borehole or extract tracer fluid to estimate properties of the subsurface At affecting chemical migration therein. The Jageler patent discloses an apparatus for testing borehole fluids. The apparatus comprises a packer, an electrical section, a hydraulic section, and a mechanical section. The Ringgenberg patent discloses a system for servicing a well, taking fluid measurements, and taking fluid samples. The system comprises a borehole packer, a pump for withdrawing fluids, a sampling chamber for holding fluids, and pressure and temperature recording devices.
The borehole and data acquisition equipment disclosed in these patents do not address the needs for multiple testing at multiple sites, some of which may be contaminated. The equipment is not transportable, easily assembled, capable of conducting multiple types of hydrologic tests or performing geochemical sampling, nor is the equipment suitable for use at sites having contaminated ground water.
In accordance with the invention, a self-contained, transportable borehole system for conducting hydrologic tests or water sampling is provided which meets the needs described above and overcomes other problems associated with the prior art.
The borehole system has a borehole unit for conducting the hydrologic tests in a borehole, and a data acquisition unit for monitoring and recording the results of the tests. The borehole unit comprises, housed in protective shrouds and connected together by union connectors in serial relation, first and second borehole packers, a plurality of pressure transducers for obtaining pressure measurements, a pump unit, located between the borehole packers, for withdrawing fluid from a test interval, and an injection unit, located between the borehole packers, for injecting fluid into a test interval. The data-acquisition unit is comprised of at least one flow meter for monitoring fluid injection by the injection unit, at least one flow meter for monitoring fluid withdrawal by the pump unit, and a data-acquisition module for providing a digital record of flow meter readings and pressure measurements.
Advantageously, the data acquisition unit further comprises rechargeable batteries for providing power for the unit and for the flow meters.
Preferably, the borehole system has a single, portable pressure source and a pressure manifold for supplying gas to operate the injector unit, to operate the transducer, and to inflate the borehole packers. Advantageously, a fluid reservoir is connected to both the fluid injection unit and to a pressure regulator which regulates the air pressure applied to the fluid reservoir during fluid injection.
The borehole system may be used for conducting measurements of ambient hydraulic pressure, fluid injection or fluid withdrawal tests for inferring formation properties, or tracer tests for inferring properties of the formation controlling chemical migration.
Preferably, the pressure transducers include an upper transducer that measures hydraulic pressure above a test interval, an intermediate transducer that measures hydraulic pressures within the test interval, and a lower transducer for measuring the hydraulic pressure below the test interval. Further, the intermediate and lower transducers are preferably located above the borehole packers.
Advantageously, the data-acquisition unit electronically stores digital records of collected data and displays the data as it is collected.
Preferably, transducer cables and pump cables are prewired in the borehole unit, and the union connectors between segments comprise screw-disconnect union ball joints.
The borehole system is very simple to decontaminate after use in contaminated ground-water or other sources of contamination, and to this end, there are provided connecting tubes made of stainless steel, polytetrafluoroethylene tubing for transporting water within the system, stainless-steel fittings, a stainless-steel pump and a polytetrafluoroethylene coated pump cable.